Furniture drive mechanisms of that type have been widely known and are used for instance as adjustment drives for adjusting the parts of a lattice array relative to one another.
EP 0 372 032 B1 describes a furniture drive mechanism of the type referred to above, comprising a pivot-mounted, pivotable swivel unit which is functionally connected to a positionally adjustable part of the furniture via a drive unit that is linked to the furniture drive mechanism in its operating state and can be moved in an axial direction along a linear axis of travel. In that earlier furniture drive mechanism the axially movable drive unit includes the nut of a spindle drive while the swivel unit is a pivot lever that is rigidly connected to a pivot shaft which in turn is functionally connected to the adjustable section of the furniture item. The spindle drive nut is in freely moving contact with the end of the pivot lever facing away from the pivot shaft.
Similar furniture drive mechanisms have also been described in DE 38 42 078 C2, EP 0 583 660 B1, DE 100 46 750 C1 and DE 100 46 752 C1.
In these earlier furniture drive designs the adjustment movement is accompanied by a change in the angular position of the pivot lever relative to the linear axis of travel of the drive unit. The resulting drawback is that the effective length of the lever arm that engages in the pivot shaft, meaning the length of the lever-arm component that extends perpendicular to the linear axis of travel of the drive unit, keeps changing during the adjustment movement, which in turn causes the force that bears on the pivot shaft and thus on the adjustable part of the furniture item during the adjustment movement to change continuously and to diminish as the effective length of the lever arm decreases. As the angle between the linear axis of travel of the drive unit and the longitudinal axis of the pivot lever grows more acute, the adjustment force exerted by the furniture drive mechanism on the adjustable part of the furniture item decreases at a correspondingly steep rate. A particular disadvantage lies in the fact that the angle grows more acute as the furniture drive mechanism approaches the end position of its adjustment movement even though that is where the force of the furniture acting on the drive mechanism, and thus the necessary adjustment force, is usually the highest.
DE 100 17 978 A1 and DE 100 17 979 A1 each describe similar furniture drive mechanisms in which, however, the drive unit is in the form of a flexible tension element such as a pull strip.
It is an object of this invention to introduce a furniture drive mechanism configured for displacing parts of a piece of furniture relative to each other, and in which the stated drawback of the conventional furniture drive mechanisms is eliminated by substantially avoiding any decrease of the adjustment force provided by the furniture drive mechanism during the adjustment movement, yet which can be produced by a simple process and thus at low cost.
This object is achieved by an electromechanical furniture drive configured during an adjustment movement, for adjusting sections of a piece of furniture relative to one another, comprising a drive unit, the drive unit being axially movable along a linear axis of travel for tilting a swivel unit, which in an operational position of the furniture drive mechanism is functionally connected to an adjustable section of the piece of furniture and can be rotated around a swivel axis, and the drive unit including an element configured for causing the drive unit to remain engaged in the swivel unit at substantially fixed point P along a linear axis of travel (30) throughout the adjustment movement.
The invention is based on the realization that the effective length of the swivel-unit lever arm changes because during the adjustment movement the point at which the drive unit engages in the swivel unit keeps shifting along the linear axis of travel of the drive unit. Accordingly, the invention is based on a concept whereby an element is provided that keep the drive unit engaged in the swivel unit at an substantially fixed point along the linear axis of travel. In that fashion, the effective length of the lever arm remains substantially unchanged during the adjustment movement and, consequently, the adjustment force exertable on the adjustable section of the furniture item by the furniture drive mechanism will remain substantially constant throughout the adjustment movement. It follows that, throughout that adjustment movement, forces of an substantially uniform order of magnitude are applied on the adjustable part of the furniture item, and most significantly in the end positions of the adjustment movement as well.
The furniture drive mechanism according to this invention is of a simple design, consequently inexpensive to produce, and rugged. It lends itself well to the adjustment of any given sections of a piece of furniture but especially to the adjustment of movable parts of a support system such as supports the slats of a lattice supporting the cushions of a chair and/or chaise lounge.
To keep the drive unit engaged in the swivel unit at an substantially fixed point along the linear axis of travel throughout the adjustment movement, the swivel unit, or a component attached to the swivel unit, is provided in the direction of rotation with an extension which is so configured that during the adjustment movement the drive unit remains constantly engaged in the swivel unit at an substantially fixed point. To that effect, the swivel unit may be provided for instance with several lever arms consecutively positioned in the direction of rotation and sequentially engaging the drive unit in such fashion that over the course of the adjustment movement the drive unit remains engaged in the swivel unit at an substantially fixed point along the linear axis of travel. In an implementation of the inventive concept that is particularly simple and thus manufacturable at low cost, the element or provisions that keep the drive unit engaged in the swivel unit during the adjustment movement at an substantially fixed point along the linear axis of travel encompass a cam-shaped guide element for the drive unit which guide element is linked to the furniture drive mechanism in its operating position. Cams of that type are particularly simple in design and correspondingly inexpensive to make, meaning that the overall furniture drive mechanism according to the invention is particularly uncomplicated and can be produced at low cost.
In another embodiment of the invention, the guide element has an substantially circular-arc profile. The guide element in that configuration is particularly simple and thus inexpensive to make.
In the aforementioned embodiment, the guide element can extend over an angle of 360°, or approximately 360°, relative to the swivel axis, with the guide element substantially having a fully circular profile. In another embodiment, of the invention, the guide element substantially constitutes the segment of a circle and, in particular, a quarter circle. For the guide element, this much of an extension in the direction of rotation is usually sufficient to ensure the engagement of the drive unit in the swivel element during the adjustment movement at an substantially fixed point along the linear axis of travel.
In another embodiment employing a guide element configured as a cam, the guide element has an substantially curved profile whereby, in the circumferential direction of the guide element, at least certain sections vary in their distance between the periphery of the profile and the swivel axis. In this embodiment the guide element and the drive unit jointly constitute a cam drive mechanism. As the curvature of the guide element changes in during constant speed of the drive unit along the linear axis of travel, the angular at which the swivel unit is rotated will change correspondingly.
Depending on individual requirements, the drive unit may be a traction or a pressure element as provided for in other embodiments.
In other embodiments of the invention, the drive unit may be flexible or substantially rigid.
In an extraordinarily advantageous embodiment according to this invention, the drive unit that engages in the guide element in the operating position of the furniture drive mechanism is provided with a toothed surface that substantially meshes with a corresponding toothed surface of the guide element. Configured that way, the guide element and the drive unit interact like a gear system. This embodiment is particularly simple and thus inexpensive to make. Moreover, it is especially sturdy and permits the application of considerable force.
In this embodiment the guide element may be in the form of a gear wheel or of a toothed quadrant as provided for in another embodiment. Gear wheels are commercially available as simple and therefore inexpensive standard products, which further simplifies the design of the furniture drive mechanism according to the invention.
In another embodiment of the above-described concept, the drive unit encompasses a chain, the combination constituting a chain drive. This embodiment as well is particularly simple and thus inexpensive to make and permits the application of considerable force.
In another embodiment of the inventive concept employing a guide element in the form of a gear wheel or toothed quadrant, the drive unit may include a toothed rack, the combination forming a rack-and-pinion drive mechanism. This configuration is again particularly uncomplicated, correspondingly inexpensive to make, and especially rugged.
In another embodiment the drive unit encompasses a rope or belt that works with the guide element, in the form of a rope drum or belt pulley, the combination constituting a belt drive mechanism. This embodiment further simplifies the design of the novel furniture drive mechanism.
The guide element may be a separate component rigidly connected to the swivel unit. However, the configuration of the furniture drive mechanism according to the invention can be further simplified by producing the guide element and the swivel unit in the form of one integral component, or with the swivel unit doubling as the guide element, as provided for in another embodiment of the invention.
The axially moving drive unit may be of any suitable design. In a desirable implementation of the inventive concept the axially moving drive unit connects to, or is constituted of, a linearly movable drive element of a spindle drive mechanism. Spindle drives of that kind are commercially available as simple, low-cost standard components, they lend themselves well to the transfer of strong forces, and they are sturdy.
The axially movable drive element of the aforementioned spindle drive mechanism may be a spindle nut which is torsionally locked but axially movable on a rotating drive spindle.
In a kinematically reversed implementation of this embodiment, the axially movable drive element of the spindle drive mechanism may equally well be an axially movable but torsionally locked spindle on which a stationary, rotationally drivable spindle nut is mounted.
In another advantageous embodiment of the inventive concept, the drive unit is attached to the swivel unit or to the guide element.
An electromechanical adjustable support system for the cushions of a chair and/or lounger and especially for the mattress of a bed are provided. Variations and further embodiments of the support system are described herein.
An inventive adjustment assembly for relatively adjustable parts of a piece of furniture is provided, as set forth herein. Appropriate, advantageous embodiments of the invention are described herein that are particularly suited for different applications and types of furniture.
Relative terms such as up, down, left, and right are for convenience only and are not intended to be limiting.